In a telecommunications system, for example a wideband CDMA system (WCDMA), there is always a desire to communicate using the least amount of power. Therefore, all transmissions should ideally be performed at the lowest possible power level, while still maintaining an acceptable quality level.
However, there are certain factors which act against this general desire to reduce power levels. Certain communication techniques have an inherent need for the power levels to be increased, both in the mobile station and the network.
For example, data compression can be used to transmit a given amount of data in less time, resulting in gaps being created to allow inter-frequency or inter-RAT (Radio Access Technology) measurements to be carried out.
In addition to the peak power being increased during the data compression, the average power also needs to be increased to compensate for the channel estimates that are not being updated during the time gaps, resulting in the receiver not being optimally tuned after the time gaps.
While increased inter-frequency and inter-RAT measurements typically have the disadvantage of increasing the average power consumption when using real time services with requirements of low delays, for example speech, they also have a degrading effect in that they reduce the available channelization-codes. During data compression a code for a lower spreading factor needs to be used, which typically blocks several codes used for higher spreading factors in the downlink.
The gaps in transmission mentioned above can also occur in other ways. For example, reducing the number of bits to be transmitted by reducing the number of extra bits which are used for error correction during some frames (i.e. code puncturing), or scheduling data transmission from a higher layer.
It is known to reduce the power requirement (and in turn improve data throughput) by reducing the number of measurements carried out in the telecommunications system. One known example of how this may be achieved is based on the use of neighbouring cell lists, and thresholds for starting measurements.
This type of solution suffers from the disadvantage that each neighbouring cell is treated equally as if they were adjacent neighbours using different antennas covering different, but to some extent overlapping, geographical areas. The reduction in these schemes is based on limiting the number of neighbouring cells included in the list, and on handover statistics and propagation predictions when cell planning is performed.
The aim of the present invention is to provide a method of estimating measurements in a telecommunications system, thereby reducing the number of measurements being performed. This has the advantage of reducing power consumption and increasing the capacity of the system.